The present invention relates to locomotive brake valve devices and in particular to such brake valve devices as are employed in transit-type electro-pneumatic brake systems.
One type of current electro-pneumatic brake equipment consists basically of a standard 26-E1 automatic brake valve, as shown and described in WABCO Publication 4208-26. Movement of the brake valve handle through its operating range controls contact closures for brake Release, Holding, Lap, Service, and Emergency functions to obtain transmission of electrical signals through trainline wires to an Application and Holding magnet valve located on each cab car and on all trailer cars when such are employed in a train. These valves in turn initiate a brake application, a brake release, or a brake holding function locally on each car of the train, thereby producing a faster brake response than would otherwise be obtained with a straight pneumatic control of the brakes. Moreover, the brake holding function has the additional advantage of permitting recharge of the brake pipe pressure following a brake application, without causing a concurrent release of the brakes except when the brake valve is moved to its release position.
Concurrently with the electrical control, the 26-E1 brake valve also initiates automatic pneumatic brake control in the various handle positions of the brake valve via the trainline brake pipe to operate the car control valves in parallel with the aforementioned electrical control. Such an arrangement provides for an automatic pneumatic back-up control in the event the electrical control fails for any reason.
It is well known that the 26-E1 brake valve, like all 26 type brake valves, is designed for pedestal mounting, as opposed to desk-style mounting arrangements generally employed today in keeping with the trend toward modernized cab design. In order to satisfy requirements for such desk-style mounting without departing from the time-proven dependability of the 26-type brake valve, a brake valve having a modular-type design that is well suited for desk-style mounting is presently being supplied to the railroads. This 30-type brake valve, as shown and described in WABCO 0.& M. Publication 4208-30, is basically similar to the 26-type brake valve, except for its modular design. Where electro-pneumatic brake control is required, additional design modifications have been incorporated to adapt it to electrical control, in the manner of the 26-E1 brake valve.